1. Technical Field
The present invention pertains to steering radio frequency (RF) beams. In particular, the present invention pertains to a device utilizing photonic crystal structures (e.g., prisms, etc.) to steer or direct RF beam transmissions.
2. Discussion of Related Art
Radio frequency (RF) transmission systems generally employ dish or other antennas that reflect RF signals to transmit an outgoing collimated beam. The beam may be steered via several conventional techniques. For example, motorized gimbal assemblies may be employed that use two motors and associated feedback circuitry to physically move the antenna (both in azimuth and elevation) to steer a radio frequency (RF) beam. However, gimbal-steered assemblies are typically heavy and bulky, and require substantial amounts of power to turn the antenna and maintain alignment of the radio beam. In many cases, the weight of the gimbal-steered assembly and antenna exceed the load rating of the platform. Further, the closed-loop feedback system used to stabilize a combined antenna and gimbal-steered assembly is complex and requires customization for each installation. In addition, gimbal-steered systems require extremely high levels of mechanical stability for applications involving narrow radio beam widths (e.g., millimeter wave radio systems).
Phased-array steering systems may also be employed to steer an RF beam. Generally, theses types of systems employ numerous transmit/receive modules that each provide a portion of the resultant RF beam. The beam portions are combined and collectively produce the resultant RF beam transmitted or steered in the desired direction. However, these types of systems require a large number of electronic subsystems (e.g., one for each radiating element or transmit/receive module) to electronically steer the beam. Phased-array beam steering systems further broaden the RF beam when moved off of boresight and increase side-lobe levels. Side-lobes are the portion of an RF beam that are a by-product of beam propagation from the aperture of the antenna. Typically, suppression of the side-lobe energy is critical for reducing the probability that the transmitted beam is detected (e.g., an RF beam is less likely to be detected, jammed or eavesdropped in response to suppression of the side-lobe energy).
In addition, dielectric wedges may be used to steer radio waves through prismatic diffraction principles. The wedges are preferably constructed from homogeneous structures. However, these types of homogenous structures require that the wedges be machined from blocks of suitable materials. Typically, this involves the machining of rectangular blocks to form wedges of a specified angle, thereby inherently wasting the material.